f Non-O1/non-O139 Vibrio cholerae inhabits estuarine and coastal waters globally, but its clinical significance has not been sufficiently investigated, despite the fact that it has been associated with septicemia and gastroenteritis. The emergence of virulent non-O1/non-O139 V. cholerae is consistent with the recognition of new pathogenic variants worldwide. Oyster, sediment, and water samples were collected during a vibrio surveillance program carried out from 2009 to 2012 in the Chesapeake Bay, Maryland. V. cholerae O1 was detected by a direct fluorescent-antibody (DFA) assay but was not successfully cultured, whereas 395 isolates of non-O1/non-O139 V. cholerae were confirmed by multiplex PCR and serology. Only a few of the non-O1/non-O139 V. cholerae isolates were resistant to ampicillin and/or penicillin. Most of the isolates were sensitive to all antibiotics tested, and 77 to 90% carried the El Tor variant hemolysin gene hlyA ET , the actin cross-linking repeats in toxin gene rtxA, the hemagglutinin protease gene hap, and the type 6 secretion system. About 19 to 21% of the isolates carried the neuraminidase-encoding gene nanH and/or the heat-stable toxin (NAG-ST), and only 5% contained a type 3 secretion system. None of the non-O1/non-O139 V. cholerae isolates contained Vibrio pathogenicity island-associated genes. However, ctxA, ace, or zot was present in nine isolates. Fifty-five different genotypes showed up to 12 virulence factors, independent of the source of isolation, and represent the first report of both antibiotic susceptibility and virulence associated with non-O1/non-O139 V. cholerae from the Chesapeake Bay. Since these results confirm the presence of potentially pathogenic non-O1/non-O139 V. cholerae, monitoring for total V. cholerae, regardless of serotype, should be done within the context of public health.
Vibrio cholerae, a waterborne bacterial pathogen, is an autochthonous inhabitant of riverine and estuarine aquatic environments. There are Ͼ200 serogroups, based on O antigenic characters, but only serogroups O1 and O139 have been associated with epidemic cholera, and both are considered a major public health threat for developing countries (1).Developed countries today rarely witness cholera cases caused by epidemic strains of V. cholerae, and outbreaks are typically travel associated (2). However, infections other than cholera can be caused by nonepidemic V. cholerae serogroups that are collectively referred to as non-O1/non-O139 V. cholerae and are generally acquired through the consumption of raw or undercooked seafood. Non-O1/non-O139 V. cholerae infections are continuously reported worldwide (3, 4), emphasizing their clinical significance. Although non-O1/non-O139 V. cholerae strains generally do not produce cholera toxin, other virulence factors contribute to their pathogenicity, including the hemolysin gene hlyA (5), the protease gene hapA (6), the cytotoxic actin cross-linking repeats in toxin gene rtxA (7), the sialidase gene nanH (8), the heat-stable toxin (NAG-ST) (9), a type 6...